This invention relates to a process to purify chemical intermediates. The chemical intermediate is oil soluble hydrocarbon sulfonic acid. The oil soluble hydrocarbon sulfonic acid can be processed with alkali earth metal bases into overbased sulfonate. The overbased sulfonate has many uses. Commonly, overbased sulfonates can be used as lubricant additives and fuel additives.
Lubricating oils tend to deteriorate under conditions of use in present day diesel and automotive engines. Deterioration is caused by acidic materials produced in engine operation, and by sludge and resinous materials which form during engine operation. Certain oil additives are used to neutralize the acidic material and to suspend damaging sludge and resin.
Highly overbased metal sulfonates have acid neutralization properties and detergent properties which suspend sludge. Overbased sulfonates contain more alkaline earth metal base than is necessary to neutralize the sulfonic acid.
Highly overbased sulfonates have been used in many lubricating oil compositions. To produce highly overbased sulfonates, pure sulfonic acid is necessary. Purification processes in the art produce sulfonic acids which contain impurities at harmful levels. The impurities can be sulfuric acid, water, reaction sludge, and calcium sulfate among others.
The impurities found in the sulfonic acid prevent successful overbasing, cause deterioration of the sulfonic acid during processing, force the use of only certain grades of metal bases for overbasing, and reduce the time the sulfonic acid and the sulfonates can be stored.
Severe engine environments caused by air pollution modifications require better oil additives. Improvements in the quality of sulfonic acid result in improved oil additives.